Polymer foam, thermoformed shapes thereof and methods of forming same

Abstract

A foam structure having a density of less than about 20 lbs/ft3. The method of forming the same comprising forming a homogeneous melt blend under pressure of a polymer member selected from the group consisting of polyetherimide resin particles, polycarbonate resin particles, a polymer blend of polyphenylene oxide and polystyrene in particle form imbibed with a blowing agent, followed by extrusion of the same into a lower pressure atmosphere. A composition comprising said particles imbibed with methylene chloride, chloroform, 1,1,2-trichloroethane or mixtures thereof. A method of thermoforming said foam in sheet form.

What is claimed is: 
     
       1. A polymer in foam form having a density of less than 18 lbs./ft 3 , wherein said polymer is a solvent imbibable linear polycarbonate wherein said solvent is a member selected from the group consisting of methylene chloride, chloroform, 1,1,2-trichloroethane and mixtures thereof. 
     
     
       2. The foam of claim 1 wherein the polycarbonate has the following chemical structure: ##STR3## 
     
     
       3. A thermoformed structure of a polycarbonate foam prepared by the method comprising: (a) subjecting a sheet of said foam having a density of less than 18 lbs./ft 3  to a first temperature sufficient to permit a shape formation to be effected therein;   (b) effecting a shape in said sheet while at said temperature; and   (c) reducing the temperature of said sheet to a second temperature permitting permanent retention of said shape in said sheet at or below said second temperature.